1. Field of the Invention
The present invention relates to a finder optical system peculariarly suitable for lens shutter type photographic cameras, video cameras, electronic cameras, etc.
2. Description of the prior art:
In general, as a finder optical system for lens shutter type photographic cameras, video cameras, electronic cameras, etc., an optical system of any of an albada type, inverse Galileo type and Kepler type (real image mode) is often used. In the past, a photometric optical system for exposure control in the use of such a finder optical system has been provided as a separate optical system, independently of a finder optical system and a photographing optical system.
Where the photometric optical system is independent of the finder optical system and the photographing optical system, as mentioned above, in order that when a photographing lens is arranged as a zoom lens or as a lens system capable of being selectively switched over to plural different focal lengths, an angle of view of light incident on the photometric optical system is changed in accordance with the variation of the angle of view caused by the zooming or the switchcover to different focal lengths, it is necessary to move a light receiving element for photometry and provide newly the zoom lens or the focal length switchable lens system as the photometric optical system. As a result, there has been problems that this arrangement brings about the increase of parts in number and is contrary to intentions of diminishing the size and reducing the cost of the camera.
Further, since optical axes of the photographing optical system and the photometric optical system are different from each other, it is necessary for the optical system to be provided with a parallax correction mechanism for the two optical axes to maintain an exact range of photometry with respect to an object located between and infinitely far position and the nearest position. This also defeats the aims of the compaction and cost reduction of the camera.